In the production of cylindrical tanks or other similar vessels, a fiber reinforced thermo-setting resin is usually applied to the exterior surface of a rotating mandrel and allowed to harden thereon. In mandrels having longitudinally slit shells, the process of removing the subsequently molded vessel from the shell has been accomplished by reducing the exterior diameter of the shell by means of power actuated cylinders or the like. These devices operate to force the normally mated longitudinally slitted edges into a second position whereby the edges are caused to overlap each other. A mandrel of the above type is shown by Lowe, U.S. Pat. No. 2,878,545; St. John, U.S. Pat. No. 3,656,732; Oswald, U.S. Pat. No. 4,233,020 and Pistole, U.S. Pat. No. 4,278,490. Each discloses longitudinally slit collapsible mandrels, of the type referred to above but having somewhat modified design characteristics. Brooks, U.S. Pat. No. 4,225,302 discloses a tank forming mandrel which is not collapsible but which includes a tapered outer molding surface for facilitating the removal of the article molded thereon. Keller, U.S. Pat. No. 1,146,263 and Morris, U.S. Pat. No. 859,681 disclose other molding apparatus comprising individual mold sections which are connected with each other so as to form elongated molding units.
There presently exists a need for a mandrel having the combined features of modular construction and collapsibility as well as structural integrity. Furthermore, such a device should afford replication of tanks or similar articles which meet exacting design specification requirements.